This is mentioned in the change log for Sublime Merge 2071, amongst other things:
Improved interface for staging/unstaging large changesets
The change sounds exciting, as it hints at my main (and only) gripe with Sublime Merge: the ability to easily select multiple files for staging/unstaging like, for example, on Git Tower: shift-select, control-select, etc.
However… I can’t seem to find anything in the documentation or on this forum that describes the “improved interface”. Any pointers please?